221640431 has 4 divisors (see below), whose sum is σ = 222141192. Its totient is φ = 221139672.

The previous prime is 221640413. The next prime is 221640437. The reversal of 221640431 is 134046122.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 221640431 - 2¹⁴ = 221624047 is a prime.

It is a super-2 number, since 2×221640431² = 98248961307731522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 221640397 and 221640406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221640437) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 249716 + ... + 250601.

It is an arithmetic number, because the mean of its divisors is an integer number (55535298).

Almost surely, 2^221640431 is an apocalyptic number.

221640431 is a deficient number, since it is larger than the sum of its proper divisors (500761).

221640431 is an equidigital number, since it uses as much as digits as its factorization.

221640431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 500760.

The product of its (nonzero) digits is 1152, while the sum is 23.

The square root of 221640431 is about 14887.5931903045. The cubic root of 221640431 is about 605.1778099043.

Adding to 221640431 its reverse (134046122), we get a palindrome (355686553).

The spelling of 221640431 in words is "two hundred twenty-one million, six hundred forty thousand, four hundred thirty-one".